Diabetes mellitus is often accompanied by impaired male and female reproductive performance in both human beings and experimental animals. Yet very little is known about the underlying endocrine-metabolic alterations responsible for these deficits. Recent work indicates that in rats experimental diabetes causes deficits in both male sexual behavior and in female sexual behavior. One portion of the proposed research will carefully characterize the effects of acute and chronic insulin withdrawal on rat sexual behavior. Related work indicates that these deficits in reproductive behaviors might be due to impaired binding of sex steroids by pituitary and brain cell nuclei, putative subcellular sites of steroid action. The other portion of the proposed research will study in vivo binding of estradiol and testosterone (and their metabolites) and steroid-receptor dynamics in brain and pituitary of diabetic rats. These experiments should provide information about the derangements in reproductive endocrinology which underlie the impaired reproductive performance of diabetics.